1. Field of the Invention
The present invention relates to storage area networks, and more particularly, to implementing read-only zones in Fibre Channel Fabrics.
2. Background of the Invention
With the increasing popularity of Internet commerce and network centric computing, businesses and other organizations are becoming more and more reliant on information. To handle all of this data, storage area networks or SANs have become very popular. A SAN typically includes a number of storage devices, a plurality of Hosts, and a number of Switches arranged in a Switching Fabric that connects the storage devices and the Hosts.
Most SANs rely on the Fibre Channel protocol for communication within the Fabric. For a detailed explanation of the Fibre Channel protocol and Fibre Channel Switching Fabrics and Services, see the Fibre Channel Framing and Signaling Standard, Rev 1.70, American National Standard of Accredited Standards Committee (NCITS), Feb. 8, 2002, and the Fibre Channel Switch Fabric—2, Rev. 5.4, NCITS, Jun. 26, 2001, and the Fibre Channel Generic Services—3, Rev. 7.01, NCITS, Nov. 28, 2000, all incorporated by reference herein for all purposes.
Fibre Channel based SANs are often organized into zones. Within each zone, Hosts can see and access only storage devices or other hosts belonging to that zone. This allows the coexistence on the same SAN of different computing environments. For example, it is possible to define on a SAN a Unix zone and a separate Windows zone. Unix servers in the Unix zone may access only storage or hosts devices within the Unix zone, and do not interfere with the other devices connected to the SAN. In the same manner, Windows servers belonging to the Windows zone may access storage or host devices only within the Windows zone, without interfering with the other devices connected to the SAN. The SAN administrator may define in a SAN multiple zones, as required or dictated by the computing and storage resources connected to it. The Switching Fabric allows communications only between devices belonging to the same zone, preventing a device of one zone from seeing or accessing a device of another zone. A host for example can access a storage device in another zone only if that storage device happens to also be in the same zone as the host.
Generally, all the host(s) in a zone have both read and write access to the storage devices in their zone. In certain situations, such as data-mining application, centralized database search operations, etc., it would be desirable to designate one or more zones in a SAN as read-only zones. In other words, each of the hosts in a read-only zone can read, but cannot write to, the storage devices in that zone. Read-only zones would be advantageous because the same storage medium can be accessed by multiple hosts while only a selected hosts can modify the storage. In the absence of read-only zones, a separate copy of the storage contents has to be created.